Airplane carburetor



Aug. 16, 1932. c, MQCK 1,871,460

AIRPLANE CARBURETOR original Filed Jan. 16, 1924 s Sheets-Sheet 1 g- 16,1932- MOCK 1,871,460

AIRPLANE CARBbRETOR Original Filed Jan. 16, 1924 s Sheets-Sheet 2 7 W a?M Aug. 16, 1932'. F. c. MOCK AIRPLANE CARBURETOR original Filed Jani 1a,1924 s Sheets-Sheet 3 Patented Aug. 16, 1932 UNITED STATES PATIENTOFFICE -FRANK ROCK, OI CHICAGO, ILLINOIS, ASSIGNOR TO IBE'N'DIXSTROIIIBERG CAR- BURETOR COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OFILLINOIS AIRPLANE cannnn'nron Original application filed January 16,1924, Serial No. 686,474. Divided and this application filed March 18,1926, Serial No. 95,517. Renewed April 11, 1929.

My invention relates to carburetors, but more especially to airplanecarburetors, and

' is a division of my co-pending application,

Serial No. 686,474, filed January 16, 1924,

which has matured into: Patent No. 1,600,008 .of Sept. 14, 1926.

The invention covers particularly improved idling and economizingarrangement and operation.

On the drawings which illustrate the various features of my inventionFigure 1 is a plan view of a double barrel carburetor;

Fig. 2 is a transverse sectional view on line 22 of Fig. 1;

Fig. 3 is a horizontal sectional view on line 3-3-of Fig. 2;

Fig. 4 is a transverse sectional view taken approximately on line 44 ofFig. 1;

Fig. 5 is a transverse fragmentary sectiona1 view taken approximately online 5-5 of Fig. 1; 1

Fig. 6 is a fragmentary sectional view through the idling tube takenapproximately on line 66 of Fig. 5;

Fig. 7 is a fragmentary sectional -view taken approximately on line 7--7of Fig. 3;

Fig.8 is a detail elevational view illustrating the adjusting arm forthe idling plug;

Fig. 9 is an elevational view of the idling plug as viewed from withinthe carburetor barrel.

The structure shown on the drawings comprises a casing 22 constructed ofa lower casing section 23 and an upper casing section 24 joining alongthe split line 25, a gasket 26 being preferably interposed between theeasing sections. It will be noted that this split line is abovethenorinal fuel level. Extending up through the lower casing section 23are the two carburetor barrels 2727, these barrels being extended upthrough the upper casing section 24. Mounted in each barrel is a Venturitube 28, and discharging ad jacent the throat of this venturi is a mainnozzle 29. A throttle valve 31 mounted on ya transverse throttle shaft32, controls the nected on the longitudinal axis of the carburetor by atube36 (Fig. 2) which quickly conducts the fuel from one chamber area tothe other whenthe carburetor is being inclined on this longitudinalaxis. Two substantially drum shaped floats 37 of equal size aresupported in the chamber areas 34 and on the arms 38 of a yoke 39. Itwill be noted that these floats are su ported with their axessubstantially coinci ent with the median plane of the carburetor betweenthe two barrels 27 The lateral portion 41 of the float chamber extendingaround the outer side of one of the barrels, receives the floatcontrolled valve 42 which maintains a predetermined level of fuel in thechamber 33. The upper end of the posite points. As shown in Fig. 7, thevalve 42 is guided in a tubular plug 45 having a valve seat in its lowerend. This valve seat faced by a hardened metal bushing 46 for engagementwith the valve 42, the tubular plug 45 being of aluminum or some otherlight weight metal.

Fuel is supplied to valve seat bushing 46 through a cored passageway 47,which ex tends diagonally across the rear part of the carburetor castingto a fuel strainer 48, as

,shown" in Fig. 3. As shown in Fig. 2, the

strainer is built up of upper and lower sheet metalca ps 49 and 51connected by a pluralityof longitudinal spacing rods 52. A cylin.drical-xscreen 53 of fine mesh encircles the cylind'rical'frame definedby the rods 52 between the end caps49 and 51. The strainer f issupported ina straining chamber 54, cast integral with the lower casingsection 23. A threaded cap 55 closes the open top of this strainingchamber and compresses a spring 56 down against the top of the strainingscreen. The fuel is admitted from the supply tank into the strainingchamber 54 through a lateral port 57, shown in plan in Fig. 1. A tube 58passes down through the "screen 48, eccentrically thereof as shown inFig. 3, and the lower end of this tube is anchored in a tubular boss 59at the bottom of the straining chamber. The supply passagewa 47 openslaterally through the wall of the oss 59 and of the tube 58 forreceiving the strained fuel fed down through the upper end of the tube58; The. spring 56 quiets all tendency of the strainer to vibrate orrattle, and by the simple removal of the plug 55 the strainer isinstantly accessible for cleaning. Its location at the rear of thecarburetor aids in retaining the carburetor of relatively narrowtransverse dimension for setting down within the V of aeronautic en'nes.

t will be observed that I have proportioned the parts so that the normalfuel level indicated on Fig. 2 by the dash and dot line X'X willlieslightly higher than the centers of the floats 37-37. This places arelatively large quantity of fuel in the float chamber,

. so that at relatively large angles of either fore or aft inclinationthere will be ample fuel to buoy up the float mechanism and to maintainthe fuel supply ports 61 leading to the fuel nozzles covered with fuel.It will also be noted that as the fuel shifts from one float chamberarea to the other through passage 36, with the fore-and aft inclinationof the craft, the lesser buoyancy of the float on the high end will becompensated for by the increased buoyancy of the float on the low end,because of the greater submergence of this low float. As before stated,the centers of buoyancy of the floats are in a median plane between thetwo carburetor barrels, and thechamber areas 34 and 35 are soproportioned on each side of the common axis of these floats that inlateral inclination of the carburetor the fuellevel will tend to revolvesubstantially around the common center of buoyancy of the float. As theresult of this there is minimum possibility of either fuel nozzle beingstarved of fuel during lateral inclination of the air craft.

sure of approximately fourteen-twelfths times the buoyancy of one floatcompletely submerged. Consequently, when in the backward or forwardinclination of the craft, the fuel rushes to the front or back,submerging one float, this totally submerged float will be incapablealone of holding the fuel valve on its seat. If two-twelfths of thebuoyancy of the other float is not supported by fuel in the other partof the float chamber, the fuel valve will open and fuel will enter untilthis two-twelfths of the float buoyancy is made up. This will raise thelevel relative to the nozzle outlet. Any proportion of floats and valvesmay be utilized to raise the fuel level a greater or lesser height.

The floats are internally braced by tubular bracing struts 60 extendingacross the same centrally. Without such braces these floats havecollapsed in service, due probably to back-fire pressures.

Fuel is supplied to the two nozzles 29 through individual ducts 61 whichopen into the bottom of the float chamber at points close to thelongitudinal median plane of the float chamber, as indicated in Fig. 3.Each duct then leads laterally out to a bore 62 which is extendedhorizontally to the lower end of the nozzle, as indicated in Fig. 5. Theouter end of each bore 62 is closed by a removable plug 63 and acalibrated plug 64 is passed through this outer end and is screwed 1ntoa thread between th bore 62 and its reduced continuation 62. T ecalibrated plug is pro vided with two similar counterbores 65 in itsends, and a short restricted passageway 66 between these bores. It willbe noted that the restricting channel 66 is set in from each end of theplug, and from the screw driver kerf in the end of the plug, so thatthere is little possibility of damaging this restricting channel 66 bythe screw driver in inserting the plug, or by any object striking theend of the plug. These 'plugs are carefully made and very carefullycalibrated as to flow before they are placed in stock, and it is quiteimportant that the same capacity of flowbe thereafter preserved. r

The duct 62 discharges into a relatively large bore 67 which is closedatthe bottom by a screw plug 68 directly below'each nozzle.

A nozzle plug 69 is inserted through the upper reduced end of the bore67, the threaded upper end of this plug screwing into a nut 71. Thenozzle in its entirety is supported upon the bridge or pair of spiderarms 72 extending across the air intake 73. The bore 62 extends throughthis bridge or spider construction, and the nut 71 screws down upon thetop of this bridge member. The nut 71 is formed with a reduced sleeve 74extending upwardly theLefrOm, and threaded at its u perend wardly fromthe sleeve 74 to form'an inter 7 9 to a point adjacent the top of thenozzle.

A metering plug 81 closes the upper end of the channel 79 and controlsthe volume of venting air which is held down through the.

channel 79 and arm 78 well 76.

Referring again to the nozzle plug 69, it will be noted that the liquidfuel is conducted through a central passageway 82, around which aregrouped a plurality of small air venting ducts 83. Both the fuelpassageway 82 and the air ducts 83 open at the upper end of the plug 69into the enlarged lower end of the-sleeve 74:, but at their lower endsthe ducts 83 open laterally into an annular groove around the body ofthe plug which communicates with a horizontal air duct 85 extending outthrough the other arm of the bridge or spider 72. During such times asthe idling jet, which I shall hereinafter describe, is in operation, theducts 83 and 85 draw fuel from the sleeve 7 'for supplying said idlingjet. Duringthe other extreme of operation, however, when the throttle isrelatively wide open the sucinto the accelerating 1 tion efi'ective atthe nozzle 29 will be higher han that effective at the idling jet, withthe result that a reverse circulation will be set up, drawing air downthrough the idling jet and idling passageway and through the ducts 85and 83 for venting into the fuel stream flowing upwardly through thepassageways 82 and 74. Attention is directed to the fact that thevertical ducts 83 ,convey this venting air up above the level of theduct 85 and to a relatively high point 1n the nozzle before mixing theair with a fuel stream. A particular advantage accrues through thisarrangement. With an air bleed type of nozzle and a submerged fuelrestriction, such as indicated at 64:, the fuel flow is proportional tothe square root of the suction across the restricting orifice, plus thegravity head from the float level to the point where the air bleedentering the emulsion passage begins to take the weight off of the fuelcolumn. To obtain a uniform mixture it is frequently desirable to reducethis last factor of the gravity head from the float level to the pointwhere the vented air enters the fuel stream. This is attained in thepresent construction by the ducts conveying this venting air up to theelevated point shown before mixing with the fuel flowing to the emulsionpassageway. Obviously, these ducts 83 can be extended up to any desiredelevation in the nozzle by extending the plug 69 up to the desired pointin the inner nozzle sleeve 74.

As above stated, the fuel flow is substantially proportional to thesquare root of the suction across the restricting orifice plus thegravity head from the float level to the point where the vented airenters the emulsion passage. The air flow is quite closely proportionalto the square root of the suction; therefore, to maintain a uniformmixture the air bleed holes entering the emulsion passage should bequite close to the fuel level.

This applies to the holes 77 from the accelerating well 76, as well asto the ducts 83. Pursuant thereto, the whole accelerating well 76 hasbeen built up close to the fuel.

level, and in giving the well its desired capacity this has meant thatthe outer dimension of the discharge nozzle 29 is relatively large. If alarge straight nozzle of this size is used in a venturi of theapproximate sizeshown,there is a tendency for the fuel to draw into theeddy space above the nozzle in an accumulation of liquid and largedrops. This I have counteracted by extending a flange 86 partly beyondthe cylindrical portion of the well and immediately below the lateraloutlet port 87 through which the fuel is discharged from the upper endof the nozzle. This flange 86 is sloped upwardly at a slight angle, andoperates to deflect outwardly from the nozzle, the air current enteringthe venturi along the sides of the nozzle body. This outwardly deflectedcurrent "of air tends to impel the fuel particles discharged laterallyfrom the ports 87 outwardly from the sides of the nozzle into the mainbody of the air stream flowing between the nozzle and the venturi. Thisaction can be augmented by sloping the top of the jet downwardly andoutwardly as indicated at 88, whereby there is induced a downward andoutward current of air off of the top of the nozzle which combines withthe laterally discharging fuel and the laterally deflected current ofair rising from the inclined shoulder 86.

A relatively narrow flange 86 will create the desired outward current ofair for securing the above results; and if the flange is too wide. thisoutward current of air will become so strong as to undesirably disturborbreak up the Venturi action. In practice I have made these flanges 86as narrow as one thirtysecond of an inch and secured the desired result.In co-operation with this design of nozzle I have employed a two-taperVenturi tube 28, such as indicated in Fig. 5. This Venturi tube has alower angle of approximately one and a halfto two degrees on a side,this lower angle being designated 1 and extending a short distancebeyond the point where the fuel nozzle discharges into the air stream.The upper angle, designated 2, is about 7 degrees on a side extendingfrom I the termination of the lower an le out to approximately thedischarge end 0 the Venturi tube. The slow taper y limits the expandingaction of the an stream at .a point where the disturbance, caused by thedischarge of the fuel, is greatest, and then the large taper allows theVenturi action to take place to a greater degree after the fuel dropletshave taken up travel substantially parallel to the air stream. Theoffset of the flan e 86 does not seriously interfere with the enturiaction, as above stated, and does give the directive eflect desired solong as the fuel spray is broken up by the venting of air into the fuelstream passing up through the nozzle tube'74. When the fuel spray is notbroken up, this relatively small offset is not suflicient to impel thelarger drops outwardly. The step of venting air into the fuel streamthus assists materially in the action of the flange 86 and the two-taperventuri 28.

The supply of fuel for the idling jet is conducted through duct 85 to anozzle 89 having a calibrated fuel passageway 91, and it will be notedthat this passa eway is submerged below the normal liquid level. Anidling tube 92 is screwed into a vertical bore 93 extending through theupper and lower sections of the carburetor casin and the lower end ofthis tube is slightly flared to receive the fuel discharged from thenozzle 89. The

, tube 92 is spaced from the bore 93 so that air may be vented downaround the outside of the tube 92 for bleeding into the fuel streamaround the lower end of the tube 92 in immediate proximity to thenozzle. Air is admitted to the annular space around the tube 92 througha plug 94 which has lateral air ports 94? communicating with thisannular space, as indicated at Fig. 6. The lug 94 is'ofiset laterallywith respect to the i ing tube and is inclined downwardly in alignmentwith the bore 95 which opens into an annular recess or groove 96 aroundthe outside of the Venturi 28. The plug 94 has a restricted orifice 97for controlling the volume of this vented air, jvhich volume can bereadily varied by the simple substitution of plugs 94 having larger orsmaller orifices.

The annular space 96 around the Venturi tube has communication throughports 98 (Fig. 4)

with a lower annular s ace 99 which opens into the lower air inta e ofthe carburetor through the slot 101 in the-central wall. The upper endof the idling tube 92 communicates with the cored passageway 102 whichextends around through the wall of the carburetor barrel to the outerside of its respective barrel. Here this passageway communicates with atransverse fuel channel 103 in the idling plug 104, substantially asillustrated in Figs. 4 and 9. This plug is formed with a reduced inner.end to form a shoulder for abutting a shoulder 105 in the boss 106 inwhich the plug is supported. A flanged.

bushing 107 screws into the outer end of this boss and supports acompression spring 108 which thrusts the plug up against the shoulder105. The inner reduced end of the idling plug opens into the carburetorbarrel27, terminating substantially flush with the wall of the barrelsubstantially in coincidence with the lower edge of the throttle 31 whenthe throttle is in closed position. As shown in Fig. 9, this end of theplug is provided with an-idling port 109 communicating with the channel103 and disposed eccentrically of the plug. It will be evident that byrotating the plug 104 this eccentrically disposed idling port can beshifted to discharge above, below, or to partially intersect the lip ofthe throttle in any one of a plurality of positions. This permits of awide graduation of the idling mixture proportions, as I shall presentlydescribe. A reduced shank or stem 111 extends through the flangedbushing 107 and has pinned thereto an operating arm 112 which is adaptedto take any one of a plurality of adjustable settings over a quadrant113. This uadrant is secured by screws between the ange on the bushing107 and the end of the boss 106. A spring detent 114 carried in theouter end of the arm 112is adapted to engage in recesses 115 in theperiphery of the quadrant 113. The provision of this outer operating arm112 enables the idling jet to be quickly and easily of the motor.

The present construction of idling system and the co-operative relationbetween the two idling adjustments is of great importance in enlargingthe size of the main venturi .in overcoming the lean spot in thetransition between idling operation and main jet operation. One of theaims of the present construction has been to provide a two-stagecarburetor, i. e., one in which the-so-called idling jet supplies thefuel over a part of the running range of the engine, which is relativelylarge as compared to previous idling jet practice. In the presentinstance this idling jet range runs from thelowest engine speed up toapproximatel 800 R. P. M., this being the first stage, and the main jetrange runs from this point on up to the highest engine speed, as thesecond stage.

In airplane practice it is desirable to increase the size of the mainventuri 28 to as large an extent as possible for maximum volumetricefliciency and for drawing in the adjusted during the operation greatestvolume of air possible at high altitud es. The chief limitationon thesize of the mam venturi hasbeen the. lean spot in the transition fromidling jet operation to main order to overcome this lean spot. I over- 1It will be evident from the foregoing thatthe two idling adjustments orcontrols cooperate to cover the entire range of idling speeds, andinasmuch as both are externally adjustable or selective, the task oftesting or adjusting the carburetor is greatly simpli- The size of theair bleed restriction 97 in fi d its relation to the size of the fuelmetering orifice 91 is a fundamental adjustment by which-the mixtureproportions for practically the entire idling range are obtainable.Moreover, this bleeding of a calibrated amount of air into the idlingcolumn of fuel considerably below the fuel level reduces the weight ofthe column and greatly extends the range of delivery of a properlyproportioned idling or first stage mixture. The ready removability ofthe plug 94. from the exterior of the carburetor without necessitatingthe removal of other plugs, screws, etc., permits of the quicksubstitution of these plugs for increasing or decreasing'the volume ofair bled into the idling system and thereby varying this fundamentaladjustment.

I find it desirable to provide a finer adjustment for the low speed endof this idling or first stage range, and, accordingly, I superpose onthis fundamental adjustment a secondary adjustment in the form of therotatable idling plug 104. As the throttle is closed down to 300 R. P.M., or the lower speeds of the motor, it is possible by rotation of theidling plug 104 to secure-the exact mixture proportion desired,regardless of inevitable variations in fit of the throttle valve, orother structural variations, or of the leakage of air into the intake.system through other points. The very high manifold suction existingduring these low engine speeds results in a higher degree of air leakageinto the manifold system through the valve guides, manifold connections,etc., than at any other speed.

As the throttle is opened up towards 800 R. P. M., or the upper end ofthe idling or first stage operation, the edge of the throttle is carriedpast the idling port 109 to such an extent that the precise location ofthis idling port will exert very little control over the idling mixture.At this time the idling mixture is controlled by the selectedrestriction of the-air metering orifice 97, relative to a predeterminedsize of fuel metering orifice 91.

Owing to the fact that the present idling system is producing anadequate, properly proportioned volume of idling fuel at the relativelyhigh engine speed of approximately 800 R. P. M., the considerablethrottle opening corresponding to this engine speed will be transmittingan eifective suction to the main Venturi, so th at the transition fromidling jet operation to main jet operation will be a blended one.

It will be noted that the idling bore 93 and tube 92 contain an amplesupply of fuel for priming, and the quick ejection of this fuel upthrough the idling jet is assured by the provision of the air bleedingpassageway 95 and plug 94. This priming supply is in= Stantly availableby closing the throttle and cranking the engine.

\Vhen the throttle is moved to open position and the main jet 29 comesinto active operation, the fuel contained in the idling system is drawnback into the main nozzle and thereafter air is bled back through theidling system into the main nozzle. This counterfiow of air occurs whenthe suction effective at the main nozzle is higher than the suctioneffective in the groove 96 around the outside of the Venturi tube. Thiscounter-flow of air can therefore be made to occur at a selected speedby connecting the groove 96 to the air passageway at the proper point.In Fig. 4 the groove is shown as connected through ports 98 and space 99to the pressure prevailing in the an entrance. By closing this openingof the groove and substituting a port which opens into the Venturi tube,as indicated in dotted-lines at 100, the suction in the groove can beraised. The particular location of this'port relative to the length ofthe Venturi will also determine the suction in the groove and theapproximate engine speed at which this counterfiow of air will begin,

Having described my invention, I claim as follows 1. In a carburetor,the combination of a carbureting chamber, a throttle controlling theflow therethrough, a plug rotatably mounted in the Wall of said chamberadjacent said throttle, an idling orifice in said plug discharging intosaid chamber, means extending from said plug to the exterior of thecarburetor, an operating member on said extending means, and detentmeans for holding said plug in adjusted position.

'2. In a carburetor, the combination of a carbureting chamber having athrottle valve therein, a plug rotatably mounted in the wall of saidcarbureting chamber adjacent said throttle valve, an idling jet in saidplug adapted to be displaced relative to said throttle by the rotationof said plug, a shank extending from said plug to the exterior of thecarburetor, an arm on the outer end of said shank, a quadrant over whichsaid arm is adapted to rotate, and means for holding said arm indifferent adjusted positions relative to said quadrant.

3. In a carburetor the combination of a carbureting chamber having athrottle valve therein, a plug rotatably mounted in the wall of saidcarbureting chamber adjacent said throttle valve, an idling port in saidplug adapted to be displaced relative to said throttle valve by therotation of said plug, a shank extending from said plug to the exteriorof the carburetor, a bushing for said shank secured to the wall of thecarbureting chamber, a spring between said bushing and said plug forholding said plug in operating po'- sition, and an actuating leversecured to the outer end of said shank.

4. In a carburetor, the combination of a carbureting chamber having athrottle valve therein, a fuel plug discharging into said chamberadjacent said throttle valve, said fuel plug being rotatable forchanging the location thereof relative to said throttle valve, a leverat the outer end of said 1plug, a quadrant secured to .the carburetorame adjacent said plug, said lever having frictional engagement withsaid quadrant to thereby yieldably lock said plug in adjusted position.

5. In a carburetor having a carbureting chamber, a throttle valve insaid chamber a main nozzle in said chamber, an idlin nozzle discharginginto said chamber ad acent said throttle, a passageway supplying fuel tosaid nozzle, an air-venting duct from said chamber, to said passagewaysaid duct opening into said chamber anteriorly of said main nozzle, andmeans for adjusting the position of said nozzle relative to saidthrottle.

- 6. In a' carburetor having a carbureting chamber, a throttle valve insaid chamber a main nozzle in said chamber, an idlin nozzle discharginginto said chamber ad acent said throttle, a priming well, afuel supplytube communicating with said nozzle and de-' pending in said well belowthe normal fuel level therein, an air-venting duct leading from a pointin said chamber anteriorly of said mam nozzle to said well and tube, and

means for adjusting-the position of said nozzle relative to saidthrottle.

In witness whereof, I hereunto subscribe my name this 9th day of March,1926.

FRANK G. MOCK.-

CERTIFICATE OF CORRECTION.

Patent No. 1,871,460. August 16, 1932.

FRANK C. MOCK. m It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Page 3, line 12, for the word "held" read bled; and thatthesaid Letters Patent should he read with this correction therein thatthe same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of November, A. D. 1932.

- M. J. Moore;- 7 I (Seal) 1 Acting Commissioner of Patents.

